Low profile kiln apparatus

ABSTRACT

The present invention relates to an apparatus (1) efficiently producing brick (53). More specifically, the invention relates to an automated, ultra low profile, continuously moving dryer, kiln and brick handling system which provides efficient, effective heating of the brick, and wherein the kiln uses only top burners (34). The invention thus eliminates the need for burners placed both on top and below the kiln or in other positions throughout the kiln, to provide effective heating.

BACKGROUND OF THE INVENTION

The present invention relates to an apparatus for efficiently producingbrick. More specifically, the invention relates to an automated, ultralow profile, continuously moving dryer, kiln and brick handling systemwhich provides efficient, effective heating of the brick, and whereinthe kiln uses only top burners. The invention thus eliminates the needfor burners placed both on top and below the kiln or in other positionsthroughout the kiln to provide effective heating.

In a typical brick making process, unfired (green) bricks are stacked onthe deck of a kiln car traveling on tracks through the kiln. The bricksare typically stacked on the kiln car in piles of about 14 bricks high.The brick stacks may have different configurations but typically thebricks are stacked so as to minimize the thickness of the stack, therebyallowing the hot gases in the kiln to more quickly and evenly heat thebrick. The brick stacks are typically arranged in rows, with rows beingseparated by a distance of 2 to 6 inches which allows better hot gascirculation resulting in quicker and more even firing of the bricks.Brick producing plants producing bricks in this manner typically use akiln firing time on the order of 30-80 hours, depending upon theparticular raw material used to make the brick. Such lengthy firingtimes are necessary due to the amount and manner in which the bricks arepassed through the kiln.

Some brick making systems use a "low profile" dryer and kiln. A typicallow profile system uses a stack of bricks from 1-8 high. Such a lowprofile system is disclosed in Applicant's prior U.S. Pat. No.4,773,850. This patent discloses a low profile dryer and kiln, incombination with low mass kiln cars carrying stacks of bricks from high1-8, which is able to utilize a greatly shortened drying and firingcycle. The present invention is an improvement over Applicants priorU.S. Pat. No. 4,773,850, the disclosure of which is incorporated hereinby reference thereto.

SUMMARY OF THE INVENTION

The present invention provides an ultra-low profile brick making system,i.e., one limited to a stack of bricks no greater than two bricks high.The invention also provides a continuously moving system, i.e., a systemwherein a load of green bricks moves continuously through a kiln withoutinterruption. Further the invention is able to achieve effective andefficient firing of the brick by providing a kiln having heatingelements or burners only in the top of the kiln. There are no burnersprovided in the bottom of the kiln, as is done in all other knowncontinuously moving kilns.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of tunnel kiln according to the invention.

FIG. 2 is a temperature profile for a kiln according to the invention.

FIG. 3 is a top plan view of a dryer used in conjunction with theinvention.

FIG. 3A is a sectional elevation of a dryer used in conjunction with thepresent invention.

FIG. 4 is a cross-section of the furnace zone in the kiln of the presentinvention.

FIG. 5 is plan view of a kiln car used in the present invention.

FIG. 6 is rear elevation of a kiln car used in the present invention.

FIG. 7 is a side elevation of a kiln car used in the present invention.

Although specific forms of apparatus have been selected for illustrationin the drawings and although specific terminology will be resorted to indescribing those embodiments in the specification appearing hereinafter,it will be apparent to those skilled in the art that the illustrated anddescribed embodiments are merely examples within the broad scope of thepresent invention as defined in the appended claims.

DETAILED DESCRIPTION OF THE INVENTION

A typical brick producing facility is illustrated in Applicant's priorU.S. Pat. No. 4,773,850. As disclosed therein raw brick material,typically comprising a mixture of clay, water and optionally other knownadditives, is formed into green bricks. The green bricks are loaded ontoa kiln car and continuously conveyed through a dryer and kiln. Inaccordance with the present invention, the bricks are stacked to amaximum of two bricks high.

Although bricks may be cut to any number of sizes, the brick ofcommercial brick comes in either 8" of 12" sizes. Individual 8" greenbricks typically have standard dimensions on the order of 2.4"×4.0"×8.6"and weigh about 5 to 6 lbs. Twelve inch green bricks typically havedimensions of 3.9"×3.9"×12.5" and weigh about 13 to 14 lbs.

The green bricks typically have a water content in the range of about 12to 16% after extrusion. If bricks having such a high moisture contentwere introduced into a kiln, the bricks would explode due to the rapidbuild-up of steam within the brick. In order to avoid this problem thebricks must first be dried in a dryer before introducing them into thekiln.

In accordance with the present invention, any dryer may be used toremove moisture from the green brick. The preferred design, operation,equipment and construction of the dryer is generally in accordance withthe following description. However, it will be recognized by thoseskilled in the art that other dryers may also be used.

Preferably, the dryer 1 is a twin track tunnel dryer, as shown generallyin FIGS. 3 and 3A. The dryer structure preferably consists of buildingbrick walls and a hollow core reinforced concrete plank roof. Sandtroughs for sand sealing of kiln cars may be provided. Hot air 10 issupplied to the dryer from the kiln by a centrifugal fan with the airdischarging into each tunnel via roof slots 12. A waste heat duct and awaste heat spill (not shown) fitted on the discharge of the dryer supplyfan may be provided to allow discharge of excess volume, if necessary. Amotorized ambient air inlet damper (not shown) is provided to allow fortemperature control of the dryer hot air supply.

Dryer recirculation is accomplished by a series of hinged, motorizedbaffles 14. The baffles preferably are located at every 3/4 car lengthalong the dryer length. The basic function of the baffles is torecirculate the air down through the load after the air flows up throughthe load by natural convection. The number of vertical recirculationsand the volume of each is controlled by the movements of the baffles.The baffles may be programmed so that each baffle can be constantlymoving to provide a wiping action to the load as well as automaticcontrol of the dryer pressure and temperature profile.

Preferably, all dryer exhaust fans 16 are mounted on the dryer roof.These may include were cool exhaust/dryer supply fans and dryer exhaustfans.

The residence time of the bricks in the dryer 1 (i.e., the drying cycle)is typically on the order of about 4-28 hours. The drying cycle of thedryer is significantly less than conventional prior art drying cycleswhich typically range from about 30 to 60 hours.

The present invention uses an ultra-low profile tunnel kiln 20 shown inFIG. 1. In one specific example of the invention described herein, thekiln design is based on the kiln longitudinal/theoreticaltime-temperature curve shown in FIG. 2. This temperature isrepresentative of the kiln atmosphere as indicated by crownthermocouples. The preferred fuel for heating the kiln is natural gas,although other heat sources may, of course, be used. The kiln isdesigned for oxidized firing, flashing or continuous reduction afterfiring to peak temperature. The kiln operates automatically in all threemodes of firing.

The kiln in its preferred form includes an entrance vestibule/air lock22. The kiln preferably is designed in 20 feet (6.1 meter) long sidewallmodules having an exterior shell of 3/16 in. thick steel sheet. Thesidewall insulation of the kiln is ceramic fiber modules. The moduleswill vary in thickness and density in accordance with zone temperaturealong the kiln as appropriate.

The kiln roof 21 is flat suspended panels of ceramic fiber modules ofthe appropriate density and thickness. The panels are approximately 5'-0(1.5 meters) long by kiln width, constructed of fiber lined expandedmetal. The kiln roof panels are bolted to the kiln sidewalls. Thisdesign allows for replacement of roof sections to add or delete burnersor roof jets, or increase sidewall height. In the event production ratesor operation requirements create the necessity for design revision tothe kiln, it can be accomplished with a minimum of difficulty anddowntime.

The kiln modules are completely constructed including refractories,fiber, burners, piping and electrical components. Modules can be boltedtogether at the plant site and all necessary connections completed.

Sand seals may be provided on each side of the kiln to minimize leakagebetween the under car area and the ware space.

The kiln is provided with two vertical lift doors not shown, counterweighted and driven by geared motor drives. The doors at the kilnentrance form a one car long entrance vestibule 22 to receive anincoming car from the dryer. The inner door will be closed at all timesexcept when a car is charged into the kiln. The outer door will beclosed only when the kiln charges a car into the offtake zone. Theentrance vestibule, with at least one door always closed, will create anair lock at the kiln entrance to minimize upsetting of the kiln draughtduring kiln car charging.

In one example of the invention, the kiln includes a preheat zone 24, afurnace zone 26, and a cooling zone 28. The kiln preheat zone 24 isapproximately nine and one half (91/2) cars long and is the earlyheating zone through which the combustion gases from the firing zone aredrawn to preheat the load. The preheat zone 24 includes a kiln offtakeportion 30 of the zone is approximately one and one half (11/2) carslong. Exhaust gases are drawn from the kiln via wall offtakes above andbelow load level via insulated stainless steel ductwork to the kilnexhaust fan. The kiln exhaust fan will discharge through an exhauststack to a suitable height above factory roof level. The kiln exhaustinlet damper is controlled by an electric motor to automatically controlkiln pressure in the firing zone. Additional control of the preheat zonetemperature is accomplished with a series of roof mounted ceramicnozzles or jets 32. In a preferred form of the invention, these nozzles32 are arranged in twenty-three rows of six nozzles per row, and eachrow has a butterfly valve for manual control. All of the nozzles 32 arelocated in the roof of kiln.

In one example of the invention, the furnace zone 26 of the kiln isapproximately eight cars long and is the heating zone in which the peaktemperature is attained. A plurality of high velocity gas burners 34 arelocated in this zone in the roof of the kiln. In the preferred form ofthe invention, a total of seventy-two high velocity gas burners will beinstalled throughout the firing or furnance zone. All of the burners arelocated above the kiln car. There are no burners below the kiln car, asin the prior known designs. The top only burner design is effective andefficient for firing bricks that are stacked two high.

The early furnace zone burners 36 preferably are located in the kilnroof in six rows of six burners across the width of the kiln. Theburners fire at an inclined angle from the flat roof toward the load,counter to kiln travel. Each row of burners is controlled as onetemperature zone via a thermocouple located in the center of the kilnroof. These burners will be oscillated in pairs of rows (three pairs oftwo rows). As the air pressure increases in row one, it will decrease inrow two, and so on through row six. As row one reaches maximum pressure,row two will be at minimum, and then the process reverse itself. Thefuel/air ratio will remain constant throughout.

The remaining furnace zone burners 38 are located in three elevatedsections of kiln roof, each with two rows of six burners firing opposedto one another, parallel to kiln travel, across the kiln width. Again,all of the burners are in the roof. There are no burners in the kilnfloor. Each pair of opposed burners is an automatic temperature controlzone across the car load. A control thermocouple is located at midpointof the elevated roof sections at each burner pair.

The burners form an oscillating combustion front which sweeps from endto end of the elevated roof section. The oscillating combustion front isaccomplished by two motorized combustion air valves operatingsimultaneously at predetermined flow rates. As combustion air pressureis increased on one end, it is decreased on the opposite end. Whenpressure reaches the maximum on one end and the minimum on the oppositeend, the process reverses. The fuel/air ratio remains constant by meansof cross connected regulator in the fuel line which receives its impulsepressure from the combustion air header. The entire combustion systempreferably utilizes Swindell Dressier's Dyna-Max™ Combustion System.This system moves the burner output gases back and forth across theload. The sweeping action of the burner flames results in an even flowof hot gases through the cross section of the load, thus increasingcombustion gas recirculation.

The oscillating combustion front enables the burners to be operated at afuel-air ratio closer to the stoichiometric than normally possible, thusincreasing efficiency of heat treating the load while minimizing the hotspotting experienced with static firing. The burners also entrain kilnatmosphere by a venturi effect, thus creating a secondary recirculatingeffect.

Temperature control preferably is by means of fuel input control withmotorized adjustable port valves. One feature of this combustion systemis that all burner gas inputs are individually adjustable by means of alimiting orifice valve in the gas line. The flows are measurable bymeans of the metering orifice. The maximum temperature in the firingzone in this example is approximately 1125° C.

In one example of the invention, after the main firing zone in the kilnthere is the cooling zone 28. The cooling zone 28 includes approximatelya one third car length "dead" zone 40 of kiln and arecuperation/reduction zone 42 which is approximately one car length.Reduction preferably is accomplished by introducing raw gas into thekiln via twenty-four lances 44 through the kiln roof, in four rows ofsix lances per row. Each gas lance is fitted with an isolating valve,limiting orifice valve and metering orifice to allow individualadjustment of gas input. The reduction zone 42 is designed to provideindirect cooling capability to allow flashed or reduced products to becooled, without injecting cooling air into the zone.

The recuperation/reduction zone 42 of the kiln provides a car lengthseparation between the furnace zone 26 and a rapid cool zone 46, whichis part of general cooling zone 28. This indirect cooling system bringspreviously unachievable control to the production of flashed and reducedproducts. The zone 46 is equipped with an alloy tube recuperator systemto work as an air-to-air heat exchanger mounted between the top of theload and the underside of the roof of the kiln.

Cooling air for the recuperator is provided by the kiln recuperation airblower. The recovered heat is used in the firing zone combustion system.The recuperation system includes a natural draft automatically damperedspill stack to provide for protection cooling flow through the tubesincase of power failure. The damper is designed to open upon power loss.

The rapid cooling zone 46 in the kiln is approximately one car long.Rapid cooling is accomplished by injecting ambient air into the kiln viaalloy jets if mounted in an elevated section of the kiln roof.

In the preferred form of the invention, a total of twelve jets areprovided, six on each side of the elevated roof section in an opposedpattern across the kiln width. The rapid cool jets are oscillated insimilar manner to the furnace zone burner system. Each air jet isprovided with a butterfly valve for individual adjustment. The rapidcool zone 46 is provided with an ambient air blower 47 and a motorizedair damper to provide automatic temperature control in the zone. Acontrol thermocouple is located at the center of this zone.

In the example discussed herein, the general cooling zone 28 furtherincludes a ware cooling zone 48 in the kiln which is approximately fiveand one half cars long. Cooling air input is provided by the exit endsupply fan. Three rows of six ceramic roof nozzles 50 inject air from arapid cool blower into the kiln, above the load of brick and counter tokiln car travel to drive cooling air down through the load. Cooling zoneroof offtakes may be provided for adjustment of cooling zone offtake airto shape the cooling zone temperature profile.

To minimize the tendency for ambient air to be drawn into the ware spacefrom between the cars and via the sand seals, an undercar pressurebalance system may be provided. An undercar exhaust fan draws air fromthe undersides of the kiln cars. The volume of air exhausted isautomatically controlled to maintain the desired pressure beneath thecars. Baffles provided beneath the kiln cars isolate the undercarsystem.

When the kiln car 52 travels through the kiln 20, the bricks 53 arestacked only to a maximum height of 2 bricks, as shown in FIG. 7.

As shown in FIGS. 5-7, preferably, the brick setting pattern in the kilncars of two high edge set brick will be supported by a brick waresupport deck 54 in an open grid pattern. This brick ware support deckwill consist of stringers 56 spanning between cordierite beams 58supported by hollow refractory posts 60 anchored into the kiln carsteelwork. This provides a level of lightweight car deck to support theload. This deck arrangement is also very open to allow for even andquick drying and firing of the brick ware.

The refractory insulation (superstructure) of the kiln car will beconstructed of the dense ceramic fiber modules. High density accordionpleated modules are placed around the car perimeter. These modules arecut closely to the kiln bench profile to provide a car side seal to thebench. The modules along the leading and trailing edge of the carproject beyond the car steel. When two cars come together these modulesadjoin and compress to form a tight radiation shield and convectionseal.

In addition to having low heat storage, the fiber kiln car designeliminates hard refractory joints at the car interior. This featureeliminates the adverse effects resulting from coating sands, brickchips, or other debris which might fall into the joints between hardrefractory pieces. With no open expansion joints for debris to collectin, fiber modules remain in place and eliminate the common displacementproblems experienced with traditional hard refractory kiln car designs.In the preferred form of the invention, the kin car refractory systemwill consist of the following: a base made from 1800° F. ceramic fiberblanket; corner modules made from pyro-log, Type "R" fiber module;perimeter modules made from 12 lb/cu ft ceramic fiber accordion pleatedmodule (2400° F.); interior modules made from 9.3 lb/cu ft 2400° F.ceramic fiber accordion pleated module; deck support made from extrudedpyrophylite or cordierite posts to support deck grid assembly; and agrid assembly made from cordieritc round, hollow stringers supported bysolid cordierite beams.

Although a preferred embodiment and specific example of the inventionhas been described, the invention is not to be limited thereto. Variousmodifications will be apparent to those skilled in the art, and theinvention is to be defined and limited only by the following claims.

I claim:
 1. An ultra low profile kiln for firing bricks stacked in akiln car traveling continuously through the kiln without stopping, saidkiln having an entrance end and an exit end and defining therebetween anultra low profile tunnel through which a kiln car loaded with bricks isconveyed, said bricks having a maximum load height on said kiln car of18 inches or less, said kiln comprising:a preheat zone through whichcombustion gases are drawn to preheat the bricks; a furnace zonedisposed behind said preheat zone, said furnace zone having a pluralityof burners for firing the bricks, said plurality of burners mounted sothat none of said burners are below the load of the bricks on the kilncar, and a cooling zone disposed behind said furnace zone and adjacentthe exist end of said kiln for cooling the bricks.
 2. The ultra lowprofile kiln of claim 1, wherein said kiln further comprises a warecooling zone located between said direct cooling zone and said exit endof said kiln for further cooling of the bricks prior to exiting saidkiln, and wherein cooling air is supplied by a fan at the exit end. 3.The ultra low profile kiln of claim 1 whereinsaid kiln includes aframework base, an insulating layer on said framework base, and a brickware support deck; said brick ware support deck being spaced from saidinsulating layer to allow heat to circulate under said deck; and saidbrick ware support deck having an open grid pattern to allow for evenand quick drying and firing of the brick ware.
 4. The ultra low profileof claim 3, wherein said insulating layer comprises a low densityinsulation made from fiber having a density less than 25 lb./cu. ft. 5.The ultra low profile of kiln of claim 3, wherein said insulating layercomprises ceramic fiber modules.
 6. The ultra profile kiln of claim 3,wherein said insulating layer comprises a base layer, perimeter modules,and interior modules.
 7. The ultra low profile kiln of claim 3, whereinsaid brick ware support deck is supported above said framework base onposts fixed to said framework base.
 8. An ultra low profile kiln forfiring bricks stacked in a kiln car traveling continuously through thekiln without stopping, said kiln having an entrance end and an exit endand defining therebetween an ultra low profile tunnel through which akiln car loaded with bricks having a stack height of 18 inches or lessis conveyed, said kiln comprising:a preheat zone through whichcombustion gases are drawn to preheat the bricks; a furnace zonedisposed behind said preheat zone, said furnace zone having a heatsource for firing the bricks, said heat source mounted so that it isabove the load of bricks stacked on the kiln car; a cooling zonedisposed behind said furnace zone and adjacent the exit end of said kilnfor cooling the bricks; said kiln car including a framework base, afiber insulating layer on said framework base, and a brick ware supportdeck; said brick ware support deck spaced from said insulating layer toallow heat to circulate under said deck; and said brick ware supportdeck having an open grid pattern comprising a plurality of beamssupported by posts fixed to said framework base, and a plurality ofstringers spanning between said beams to allow for even and quick dyingand firing of the brick ware.
 9. An ultra low profile kiln assembly forfiring bricks stacked in a kiln car, said kiln assembly comprising:akiln having an entrance end and an exit end and defining therebetween anultra low profile tunnel through which a kiln car loaded with bricks isconveyed continuously without stopping; a kiln car adapted to beconveyed continuously through said kiln without stopping; a load ofbricks stacked on said kiln car to a load height no greater than 18inches; said kiln having a plurality of burners for firing said bricksin said kiln, said burners mounted in said kiln so that none of saidburners are below the load of said bricks on said kiln car.